In a chilled mixing bowl, combine heavy cream and powdered sugar. Whip on medium-high speed until stiff peaks form (about 3-5 minutes). Refrigerate the whipped cream until serving.

In a large mixing bowl, whisk together all-purpose flour, baking powder, salt, white sugar, and yellow cake mix until combined and clump-free.

Add vanilla extract, egg, and melted butter to dry ingredients. Gradually whisk in whole milk until just combined; some lumps are fine.

Gently fold in rainbow sprinkles with a spatula, being careful not to overmix.

Preheat a non-stick skillet over medium heat and lightly grease it. It's ready when water sizzles upon contact.

Drop batter onto the skillet in 3-4 inch circles. Cook for about 3 minutes or until edges bubble and turn golden. Flip and cook for an additional minute.

Keep pancakes warm in a 250°F oven while cooking the remaining batter. Serve with whipped cream and additional sprinkles.